The following information was written by me on the Ragwing internet group:

There has been questions that periodically arise concerning the strength of a Ragwing airplane, specifically the wing and how many G’s is can withstand.

By just referring to a set of plans from Herb Beaujon, which includes basic equations for calculating stresses on standard spars, we can do a simple formula to check the stress and figure out if an RW11 (or any other Ragwing plane for that matter) can handle up to 4 G’s which is typically the minimum level of strength you want in any airplane.

For kicks I went through and did the calculations:

The RW11 has a gross weight of 850 lbs.
Wing span of 28 ft (or 336 inches)
Wing should be able to carry +4 G’s (4 x’s gross weight or 3,400 lbs)
I’m “Guessing” that the outside wing panel is 80″ from strut connection point to wing tip (COMPLETE GUESS), so this measurement could change the equation to some degree if my assumption is wrong.

The front wing spar must support 75% of the load, and the rear spar 25%.

To be strong enough for +4 G’s, The outside wing panel length of 80 inches would need to support 202.38 lbs. This is found by taking that section 80/336=23.8% of the gross weight, or .238 x 850 lbs = 202.38 lbs. Further, the front spar carries 75% of this load or .75 x 202 = 151 lbs.

From the graph I have from Herb Beaujon’s packet, this would require a spar built very similar to a Ragwing spar to support the wings under 4 G’s. Likely Ragwing Spars would carry slightly more. However, more strength could be added to Ragwing spars by making them a full box spar (putting the plywood web on the back side as well).

Also since Ragwing Spars are very very similar to Team aircraft spars, Fisher Spars, Loehole Spars, and many other wood and fabric planes, we can only assume that this is a tried and true design.

So unless the plane is built incorrectly, or the pilot is pulling some heavy G’s doing acro, they should be solid planes.

- Jeff
(I’m not an engineer, just a collector of airplane plans)